Sunday 23 June 2013 16.56 EDT
First published on Sunday 23 June 2013 16.56 EDT

Weather is what happens. Climate is the sum of what happens, averaged over a generation or more. The unpromising start to the British summer, and the apparent recent trend towards cool, wet summers, are just that: an unpromising start, and an apparent trend. Neither is in itself an indicator of climate change. Rain in June does not mean that global warming is not happening. A succession of disappointing summers does not mean that in a warmer world Britain can expect mild winters and wet summers as a matter of course. The Met Office conclusion that Britain might be caught in a natural cycle of cooler summers with more rainfall than usual – and that describes six of the past seven summers – is just a reminder that climate is the long-term average of ups and downs.

It has become increasingly possible to make connections between ocean surface temperatures, or aerosol distribution in the atmosphere of the northern hemisphere, or shifts in the jet stream, or reductions in the Arctic ice cover, and changes in regional weather patterns, but these things are still only associations, tentative connections that seem to make sense. Predictions based on good observations of these connections can still turn out to be gloriously wrong: in April 2012, a hosepipe ban in expectation of severe and extended drought was the cue for the wettest summer in a century. Climate is an observed pattern, and farmers place their bets on climate's overall probabilities. Day-to-day weather, especially in a maritime climate, is chaotic.

Some things, however, remain clear: Britain is a warmer place than it used to be. The United Kingdom is on average about 1C warmer now than it was in 1970. Spring on average arrives two weeks earlier than it did 30 years ago; autumn has been delayed a week. Britain's native trees now fruit 18 days earlier than they did even a decade ago, according to the Woodland Trust. Flowering has advanced an average of five days for each one-degree rise in temperatures. Red mullet, that Mediterranean delicacy, is now caught off British coasts.

According to World Meteorological Organisation calculations, 11 of the 12 warmest years ever recorded have fallen in this century, and although the rate of increase in global temperatures seems to have slowed in a way that doesn't square with projections, climate scientists still expect this decade to be on average warmer than the previous one, and the next to be warmer still. Other countries must face heat waves, forest fires, catastrophic floods, terrifying tornadoes, tropical storms and extended drought, and there is little sign that governments anywhere are prepared for concerted action. If a typical British summer is the worst that befalls us this year, we should be thankful. There could be much worse to come.